Stacking of integrated circuits has long been an available technique for increasing functionality for a given amount of space. For example, this has been a technique for doubling the amount of memory by stacking two memory integrated circuits. It has now become more desirable to use stacked integrated circuits that are of a different type because of the different manufacturing techniques used for the different functions. For example, rf circuits are often needed to be used in conjunction with logic circuits but the manufacturing techniques are quite different for these different functions. Thus, it is more practical to stack these two functions than try to achieve them both on the same integrated circuit. In stacking die, issues arise relating to the interconnection between different die or between die and a wafer that are not present with regard to a single die. A pad often called a micropad is useful in performing the die to die or die to wafer connection. Thermocompression bonding of micropads from two different die or wafers provide both mechanical and electrical inter-strata connections of the stacked die. Some of the difficulties associated with micropads relate to the processing which typically includes electroplating. One problem is undercutting of the pads and another is oxidation of the metals, e.g., copper/tin (Cu/Sn) that are commonly used.
Therefore, there is a need for an improvement in interconnect pads.